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由于试件制备简单、试验便于操作,巴西劈裂试验被广泛用于测量岩石的抗拉强度,但试验结果易受细观结构、平台中心角、端部摩擦等因素影响。针对上述问题,本文对花岗岩进行矿物成分鉴定,采用数字图像技术表征试件的真实结构,建立了颗粒离散元的岩石细观力学模型,利用该模型对花岗岩的劈拉试验进行了数值仿真,并通过开展相应的试验论证了模型的可靠性。同时,基于数值模型研究了平台中心角以及加载端部边界效应对花岗岩劈拉破坏的影响。研究表明,随着平台中心角的增大,花岗岩试件中心的拉应力降低,压、拉应力比增大,中心角取20°~30°为宜;此外,端部摩擦效应随着平台中心角的增大而增大,当中心角小于30°时,端部摩擦影响较小,可忽略不计。
Due to the simple preparation of the test specimen and the convenient operation of the test, the Brazilian cleavage test is widely used to measure the tensile strength of the rock. However, the test results are susceptible to the effects of mesostructure, platform center angle and end friction. In order to solve the above problems, this paper identified the mineral composition of granite. The digital image technique was used to characterize the real structure of the specimen. The micromechanical model of granule discrete element was established. The splitting experiment of granite was numerically simulated by the model. The reliability of the model is demonstrated through the corresponding experiments. At the same time, based on the numerical model, the influence of the central angle of the platform and the loading end boundary on the splitting failure of granite was studied. The results show that with the increase of the central angle of the platform, the tensile stress in the center of the granite specimen decreases, and the ratio of the compressive and tensile stresses increases. The center angle of the specimen is 20 ° ~ 30 °. In addition, the friction effect of the end decreases with the center of the platform The angle increases and increases, when the center angle is less than 30 °, the impact of the end friction smaller, negligible.